A container refrigeration system configured to cool an inside of a container has been known as a refrigeration system configured to perform a refrigeration cycle. Patent Document 1 discloses the container refrigeration system of this type.
The container refrigeration system disclosed in Patent Document 1 includes a refrigerant circuit in which a compressor, a condenser, an expansion valve, and an evaporator are connected together. The evaporator is provided inside the container. In the evaporator, refrigerant is evaporated by absorbing heat from air inside the container. In such a manner, the air inside the container is cooled.
In the refrigerant circuit of the container refrigeration system, a bypass circuit configured to supply refrigerant (so-called “hot gas”) compressed in the compressor to the evaporator without passing through the condenser is provided. Specifically, the bypass circuit includes two bypass pipes and two opening/closing valves provided respectively for the bypass pipes. Each of the bypass pipes allows communication of a gas line between the compressor and the condenser with a liquid line between the expansion valve and the evaporator. In the container refrigeration system, the foregoing bypass circuit is used to perform a defrosting mode for defrosting the evaporator.
Specifically, in the defrosting mode, a defrosting capacity is adjusted to two levels depending on an opening/closing state of the two opening/closing valves. That is, when only one of the opening/closing valves is opened in the defrosting mode, hot gas is supplied to the evaporator only through corresponding one of the bypass pipes. Thus, the flow rate of refrigerant flowing through the evaporator is relatively low. A heating capacity (defrosting capacity) inside the container is also relatively low. On the other hand, when both of the opening/closing valves are opened in the defrosting mode, hot gas is supplied to the evaporator through the two bypass pipes. Thus, the flow rate of refrigerant flowing through the evaporator is relatively high. The heating capacity (defrosting capacity) inside the container is also relatively high.